The goal of this research is to conduct a cross-cultural genetic and epidemiologic study of a variety of health-related variables in the families of 540 pairs of U.S. white, U.S. black, and Norwegian monozygotic twins. The unique genetic relationships contained within these kinships will be used to resolve the genetic, environmental, and maternal determinants of selected anthropometric, biochemical, psychological and genetic traits. A major focus will be the inheritance of heart disease risk factors including blood pressure, cholesterol, Factor VIII, the levels of the serum apo A-I, and A-II, apo B, apo E3, and apo E4, lipoproteins as well as the reserve cholesterol binding capacity. In each of the three racial subgroups, two high-risk and a control sample of 60 MZ twin kinships will be drawn from existing population-based twin registries in Virginia and Norway. The high-risk families will include MZ kinships in which there is a history of hypertension or coronary disease in the parents of the twins, but no such history in the parents of spouses; while the control families will include kinships with no history of heart disease in the parents of either the twins or the spouses. A comparison of the distribution of variation of heart disease risk factors in the offspring of the high-risk and control families will permit a more detailed analysis of existing evidence that maternal effects influence several risk factors and the application of new tests for the detection of major gene effects on heart disease risk factors. An important goal of the research will be the testing and modification of existing methodologies for the analysis of MZ twin kinship data and a cross-cultural comparison of the causes for phenotypic variation in three ethnic groups located in two quite different geographic areas of the world.